The present invention relates generally to systems and methods for digital signal processing, and in particular to systems and methods that are suitable for performing thermoreflectance measurements with enhanced spatial and temperature resolutions.
Themoreflectance is a well-established non-contact method for measuring temperature distributions on a variety of different sample types. In the past decade, thermal imaging (as opposed to single point measurements) has become increasingly popular. As a result, different ways to achieve this goal have been published. There is a consensus in the recent literature (as recent as January 2005) that the quantization limit of an n-bit CCD, typically utilized for detecting reflected photons in thermoreflectance measurements, limits the detectable change in the reflectivity, and therefore seemingly limits the temperature resolution of the measurements.
In many thermoreflectance measurement systems, as well as in a variety of other systems, analog to digital conversion (ADC) is employed to convert an analog signal (i.e., allowing floating point results) into a digital one (i.e., only using integer numbers). The smallest digital unit is known as the least significant bit (LSB), or, in the language of signal conversion, the code. The code, when combined with the analog-digital conversion factor, yields the smallest detectable (analog) signal change, also called the code width. It is well established that for single channel ADC, a method known as “oversampling and averaging” can increase the effective number of bits of the ADC. Devices based on this principle are commonly known as “ΣΔ ADC”, “sigma delta ADC” or a similar nomenclature.
Conventional thermoreflectance systems and methods, however, suffer from a number of shortcomings. For example, the spatial resolution achieved by conventional infrared imagers operating based on black-body emission is typically limited to ˜5 microns while the temperature resolution of such systems is in a range of few hundred mK to 1K.
Hence there exists a need for enhanced methods and systems of digital signal processing. There is also a need for such methods and systems that allow performing thermoreflectance measurements with improved spatial and temperature resolution.